This invention relates to the field of electrical outlet boxes having self-contained clamping means to mount and secure the boxes in corresponding apertures provided in a wall panel of a structure (such as a house or mobile home) in preparation for wiring for electrical service.
For many years, outlet boxes were secured to studs and other portions of a building wall by nails or screws, and many are still secured by this method. In certain types of building construction such as pre-fabricated housing, manufacture of mobile homes and the like, assembly line techniques are employed which lend themselves to time and labor saving techniques. Thus, various self-contained clamping devices have been incorporated into electrical outlet boxes to enable securing the box in place in an aperture in a wall panel without the need for using screws or nails driven into the studding framework. Among such self-contained clamping devices are winglike members mounted on a frontal access screw to rotate upon rotation of the screw from a folded position along a side of the box after the box has been inserted in a receiving aperture in a wall panel to an extended position wherein the winglike member extends outwardly from the side of the box to sandwich an edge of the wall panel between such member and a frontal flange of the box. Such clamping devices rotate on an axis which is normal to the open front wall of the outlet box and normal to the wall panel in which the outlet box is being secured. The bearing surface of such devices which faces the front of the box remains the same both in the folded position against the side of the box and in the extended position when rotated outwardly to bear against the rear surface of the wall panel after the box has been inserted in the aperture in the wall panel. If this front facing bearing surface is made relatively broad for good clamping contact when in the extended position, the device will not clear when the box is inserted into the receiving aperture. If the front facing bearing surface is made narrow enough to clear when inserting the box in the receiving aperture in the wall panel opening, it provides only minimal clamping contact when rotated outwardly from the side of the box to its extended position. Accordingly, when using this type of device it is customary to provide one such device in each corner of a rectangular outlet box in order to provide some degree of stability to the box when installed.
Other attempts to provide self-contained clamping devices for electrical outlet boxes have included forming integral ears or clamping surfaces as outward projections from wall portions of the outlet box, with a cam surface positioned to contact a corresponding wall panel edge bounding the aperture in the wall panel as the box is pushed into such aperture to flex the integral ears or clamping surfaces inwardly until they are pushed beyond the rear surface of the aperture of the wall panel whereupon they are supposed to spring back to bear against such rear surface and clamp the box in place with the wall edges held between such clamping surfaces and frontal flanges of the box. This type of self contained device requires the use of materials capable of flexing the clamping surfaces inwardly when the box is being inserted and springing back when fully inserted. When used with metal boxes, the cammed ears must be relatively thin to enable them to flex inwardly when the box is pushed in the aperture in the wall panel, thus limiting the area of bearing surface available to clamp against the rear surface of the wall panel. When this type of device is used with various types of plastic outlet boxes, the cammed ears do not always return to the fully extended position and hence do not provide a satisfactory clamping surface.
The present invention overcomes the problems associated with such prior art self-contained clamping devices. The L-shaped clamp members described herein pivot between retracted and clamping position on an axis which is parallel to the open front wall of the box and to the surface of the wall panel in which the box is mounted. This enables the use of the clamp which has a relatively broader bearing surface than devices which rotate on an axis normal to the surface of the wall in which the box is mounted. A more secure clamp of the box to the wall panel can thus be achieved, and with fewer clamp devices thus reducing cost.